1- cell structure

Question 1

1cm -> 10mm
how to get to micrometres, nm

Answer 1

x 1000

Question 2

why are electron microscopes better resolution than light

Answer 2

• electron wavelength shorter than wavelength of light
  x 250000 mag
  (0.5nm res)

light
x1500 mag

Question 3

magnification + resolution difference

Answer 3

mag: how many times image larger than original
res: smallest distance between 2 points where 2 points can be distinguished

Question 4

-ve of electron microscope

Answer 4

• extremely expensive
• more elaborate sample prep required
• can’t observe live specimens bc sample needs to be dry+unmoving
• can’t observe colour since electrons are colourless

Question 5

how to observe cells at high power

Answer 5

• locate specimen using low power objective lens
• focus using low power objective lens BEFORE high power objective
• only use fine focus with high power objective

Question 6

Describe how a transmission electron microscope works to give a higher image resolution.

Answer 6

• electrons pass through thin specimen
• denser parts absorb more electrons
• denser parts appear darker
• so high res bc short wavelength

ALWAYS mention wavelength when talking abt resolution

Question 7

-: of TEM

Answer 7

• must be in vacuum
• specimen must be very thin
• artefacts present
• complex staining method

Question 8

Describe how to make a temporary mount of plant tissue when using an optical microscope.

Answer 8

• add drop of water to glass slide
• obtain thin section of plant tissue and place on slide / float on water drop
• stain with iodine in potassium iodide
• lower cover slip using mounted needle

Question 9

Describe the function of the nucleus in non-dividing cells

Answer 9

• contains chromosomes/DNA/gene (coded info for DNA synth)
• contains sequence of bases in DNA
• site of transcription+translation
• makes ribosomes

Question 10

cell wall material: prokaryotes, fungi, plants

Answer 10

murein, chitin, cellulose

Question 11

vacuole

Answer 11

maintains pressure inside cell- turgidity
stores food reserves/waste

Question 12

Roles of CSM

Answer 12

• selectively permeable barrier(between cytoplasm+external environment)
• receptors for cell signalling
• cell recognition with cell surface antigens

Question 13

What are the key differences between prokaryotic and eukaryotic cells?

Answer 13

Prokaryotic cells: No nucleus, circular DNA, 70S ribosomes, few organelles, small (0.5–5µm).
Eukaryotic cells: Nucleus, linear DNA, 80S ribosomes, many organelles, larger (40µm)

Question 14

function of Golgi Apparatus (lipid+protein)

Answer 14

processes+package: cisternae
store+transport: vesicles
synthesise lysosomes: specialised vesicles

Question 15

function of lysosomes

Answer 15

contain hydrolytic enzymes to break down waste+old organelles

Question 16

RER

Answer 16

Transports proteins, covered in ribosomes

Question 17

SER (lipids+carbs)

Answer 17

Synthesises+stores lipids (cholesterol+steroids), no ribosomes
- detoxification

Question 18

lysosomes

Answer 18

digest pathogens+break down waste
hydrolytic enzymes, surrounded by membrane to keep enzymes separate from cell

Question 19

What is the evidence for the Endosymbiotic Theory?
(theory that mitochondria and chloroplasts originated as free-living bacteria that were engulfed by a larger cell)

Answer 19

Mitochondria and chloroplasts have their own DNA, double membranes, 70S ribosomes, and replicate like bacteria

Question 20

cytoskeleton: made of

Answer 20

microfilaments, microtubules, and intermediate filaments
provides structure to cell

Question 21

microfilaments

Answer 21

Made of protein actin.
Involved in cell movement and locomotion, such as crawling and muscle contraction

Question 22

microtubules

Answer 22

Made of protein tubulin.
Form scaffold-like structure throughout the cell.
Form the main component of the mitotic spindle, used for cell division.
Act as tracks for intracellular transport of vesicles and organelles.

Question 23

intermediate filaments

Answer 23

Maintain the position of organelles within the cell.
Responsible for the mechanical strength of certain tissues, such as the skin and hair.

Question 24

CW

Answer 24

• supports cell
• prevents cell from bursting- can withstand osmotic pressure
• allows substance exchange between cells(plasmodesmata)

Question 25

vacuole cell sap(salts, sugars)

Answer 25

Helps to maintain pressure within the cell, which keeps the cell rigid and stops the plant from wilting

Question 26

algal+fungal can be uni/multicellular

Answer 26

algal chloroplasts are diff shape fungal cells dont have chloroplasts

Question 27

prokaryote capsule

Answer 27

extra layer around CW made up of polysaccharides, **protects** cells from attack by antibiotics or white blood cells

Question 28

pili

Answer 28

hair-like structures attaching prokaryotic cells to other cells/surfaces

Question 29

always present in virus (2)

Answer 29

genetic material: DNA/RNA (single/double) **capsid**: layer of *protein* molecules surrounding+protecting genetic material

Question 30

sometimes present

Answer 30

envelope (phospholipid) glycoproteins (help viruses bind to host cells) enzymes (allows them to convert RNA into DNA)

Question 31

functions of DNA in chloroplast

Answer 31

- code for proteins/enzyme rubisco - allows mRNA transcription

Question 32

organelles that CAN be viewed under a light microscope

Answer 32

- mitochondria(visible but unclear) - nucleus

Question 33

organelles smaller than 200nm that CAN'T be viewed

Answer 33

- ribosomes - lysosomes - endoplasmic reticulum

Question 34

organelle size from largest to smallest

Answer 34

nucleus -> mitochondria -> ER -> lysosome -> ribosome

Question 35

max useful magnification of light, electron microscope

Answer 35

x1500 x500, 000

Question 36

resolution limit of light, electron microscope

Answer 36

200nm 0.2nm

Question 37

eyepiece lens magnification is

Answer 37

x10